//---------------------------------------------------------------------------------
// Copyright (C) 2008 Chillisoft Solutions
// 
// This file is part of the Habanero framework.
// 
//     Habanero is a free framework: you can redistribute it and/or modify
//     it under the terms of the GNU Lesser General Public License as published by
//     the Free Software Foundation, either version 3 of the License, or
//     (at your option) any later version.
// 
//     The Habanero framework is distributed in the hope that it will be useful,
//     but WITHOUT ANY WARRANTY; without even the implied warranty of
//     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//     GNU Lesser General Public License for more details.
// 
//     You should have received a copy of the GNU Lesser General Public License
//     along with the Habanero framework.  If not, see <http://www.gnu.org/licenses/>.
//---------------------------------------------------------------------------------

namespace Habanero.Base
{
    /// <summary>
    /// An interface to model a generator of unique numbers. It keeps
    /// record of the last number retrieved and can provide a new
    /// unique number on request.  An example usage might be a till
    /// receipt number for a retail business.  Incrementing the numbers
    /// as they are dispensed is one means of achieving uniqueness.
    /// </summary>
    /// need to apply concurrency control to ensure new number not retrieved
    /// by another user before first user saves and updates number (could
    /// update immediately)
    public interface IDBNumberGenerator
    {
        /// <summary>
        /// Returns the next available unique number. One possible means
        /// of providing unique numbers is simply to increment the last one
        /// dispensed.
        /// </summary>
        /// <returns>Returns an integer</returns>
        int GetNextNumberInt();

        /// <summary>
        /// Creates a database transaction that updates the database to the
        /// last number dispensed, so the next number dispensed will be a
        /// fresh increment
        /// </summary>
        /// <returns>Returns an ITransactional object</returns>
        ITransactional GetUpdateTransaction();
    }
}